Ординатура / Офтальмология / Английские материалы / Eye Essentials Assessment and Investigative Techniques_Doshi, Harvey_2005

Slit-lamp examination of the anterior segment

lesions. At low magnification, blink pattern should be readily

50assessable and this may give the practitioner clues about symptoms relating to dry eye either in contact lens wear or otherwise.When moving across the eyelids the practitioner may utilize a ‘Z’ or zigzag pattern to examine their surface; moving from one lid to the other (upper to lower or vice versa).

By switching to direct illumination with a more focused beam and higher magnification (10–16×), the practitioner should then assess the lid margin, looking for signs of blepharitis.This tends to appear as either an anterior or posterior form.The latter is more commonly known as a meibomian gland dysfunction. Anterior blepharitis may be either Staphylococcal or seborrhoeic in origin.

Staphylococcal blepharitis typically affects patients with atopic eczema and is more common in females and younger patients. The lid margins are hyperemic and show telangiectasis.There may also be scaling, which forms collarettes around the base of the eyelashes.Where these have been removed, small, bleeding ulcers may be present.This form of blepharitis is caused by bacterial infection of the base of the eyelashes and may be a relative contraindication to contact lens fitting.

A number of complications associated with Staphylococcal blepharitis may be noticed including whitening or complete loss of lashes, trichiasis or scarring of the lid margin. If the infection spreads then styes may result. Internal hordeola appear when the infection spreads to the meibomian glands. All of these lesions are visible using diffuse and direct illumination techniques.The exotoxins produced by the bacteria may disrupt the tear film integrity and also irritate the palpebral/tarsal conjunctiva resulting in hyperemia. Marginal corneal infiltrates may also be apparent which over the long term can lead to pannus and scarring. Management of the condition usually involves performing a strict lid hygiene regimen. Occasionally, in more severely inflamed eyes, referral to a general practitioner for antibiotic/anti-inflammatory drop combination such as Tobradex, may be necessary.

The seborrhoeic variety tends to be associated with a with seborrhoeic dermatitis, which usually affects the scalp, face and chest.The symptoms are not as marked as the staphylococcal form, the hyperemia and telangiectasis are milder and the scales

General examination of the eye

are often greasy but do not lead to bleeding when removed.

There are dry or greasy forms. Management involves good lid 51 hygiene and lid scrubs with a degreasing agent, such as an

aqueous solution of sodium bicarbonate.

Posterior blepharitis is arguably the less severe of the two forms. It can be subdivided into meibomian seborrhoea and meibomianitis. Meibomian seborrhoea causes hypersecretion from dilated meibomian glands.The lid margins may show small oily globules or waxy collections.The tear film may show excessive debris (Figure 4.3), usually oily and there may be a foamy/frothy discharge along the lid margins or in the canthal areas. Expressing the meibomian glands results in excessive matter being discharged into the tear film. As this is different to the composition of the normal secretions of the meibomian glands, mild irritation of the conjunctiva often occurs.The patient typically complains of a burning sensation, as the secretion affects the normal stability of the tear film.

Figure 4.3 Excessive debris in the tear film as a result of posterior blepharitis

Slit-lamp examination of the anterior segment

Meibomianitis involves inflammation at the gland orifices.The

52openings may become irregular and are often capped by an oily/waxy matter. Expression of the glands is difficult and any matter expelled may be thick and contain particles, which in some cases resembles toothpaste. If the contents of the glands become trapped, meibomian cysts may form. A papillary conjunctivitis and punctate keratitis may also occur.

With particles being shed into the tear film, its stability is disrupted. Management of the condition involves lid scrubs and possible referral to a general practitioner for oral antibiotics, typically tetracycline-based drugs.Treatment may take anything between 1 and 6 months.

Examination of the tear film

The tear film is arguably the most underexamined ocular structure during a general examination of the ocular surface. Many symptoms of ocular discomfort or asthenopia can be attributed to deficiencies in the tear layer.The tear film is essentially a trilaminar structure consisting of: a mucin layer (closest to the cornea), an aqueous layer and a lipid layer (closest to the surface). Anomaly of any of these layers can result in the patient experiencing symptoms. It is normal for the tear film to be examined following the instillation of sodium fluorescein in blue light (produced by the cobalt blue filter), however, with the reduction in the amount of ambient light produced by this technique some subtle changes to the tear film may be missed.

Diffuse illumination and low magnification offer a good overview of the tear film.This allows the clinician to observe any debris in the layer. Direct illumination or an optical section can then be utilized to investigate detail. Debris in the tear film often appears as particles and can be indicative of blepharitis (see above).The particles are often easily seen with direct (and indirect) illumination as they readily reflect light (Figure 4.4). Large particles often show up well with retro-illumination

(Figure 4.5). Particle movement should also be observed. In the normal tear film particles on the surface move slower than deeper ones as a result of surface tension. If the movement of

General examination of the eye

53

Figure 4.4 The particles in the tear film with direct (and indirect) illumination as they readily reflect light

Figure 4.5 Large particles in the tear film often show up well with retro-illumination

Slit-lamp examination of the anterior segment

particles is too fast, a thin, watery tear film is indicated. Immobile

54or slowly moving particles indicate excessive viscosity of the tear film. Such a tear film may show interference fringes during specular reflection. As the patient blinks these emerge, like waves, from the lower lid margins.

The tear prism can be seen by direct illumination.This is typically 0.2–0.5 mm high in the center and tapers off to approximately half this height in the periphery. If drainage of the tear film is compromised by a blockage at the puncta or further in the lacrimal drainage system, the tear meniscus height may be significantly greater.This can result in epiphora and may be an important consideration when fitting a patient with a contact lens.

Instilling fluorescein is an invasive method of assessing the tear film. As such there is some alteration to the normal structure of the tear layer. Normally it drains completely from the eye in around 2 minutes. Older patients may take longer as stenosis of the punctae occurs to offset reduced aqueous production. If the drainage of fluorescein takes longer, or if there is significant difference between the two eyes blockage of the drainage system may be suspected. If this is suspected the puncta should be examined. Irregularity of the puncta can indicate canaliculitis. Management of a blockage of the lacrimal drainage system involves punctual massage in the early stages but may require syringing in the latter stages.

Excessive tearing is a hindrance to the patient and is of course clinically relevant. However, insufficient tears tend to give rise to more symptoms and signs. A depleted tear film may give an indication of a tear layer deficiency. Clinicians regularly determine the tear break-up time (TBUT) once fluorescein has been instilled, a procedure familiar to most readers.The eye is illuminated with a broad beam and the cobalt blue filter is in place. Low magnification is used.The patient is asked to blink normally a few times and then ask not to blink.The time taken for dark spots or streaks to appear is noted.This indicates a break-up of the tear layer. Normally, this would take 15–20 seconds, any figure below 10 seconds is deemed to be abnormal and indicative of a dry eye.Where the same area consistently breaks-up rapidly, there is likely to be a surface irregularity rather than a dry eye.

General examination of the eye

The clinician should investigate this further using direct

illumination, optical section and high magnification. 55 TBUT can also be measured non-invasively using instruments

such as the Tearscope or the mires in a keratometer. Patients with dry eye often have mucus strands/globules and debris in their tear film.This occurs as the mucin layer becomes contaminated with the lipid layer as the tear film breaks up. In severe cases mucin may interact with cellular debris to form filaments, which attach to the epithelial surface and move with every blink. Fluorescein staining may indicate a punctate epitheliopathy.

Examination of the conjunctiva

As with the lids and tear film, the best way to obtain a general view of the conjunctiva is to use diffuse illumination and a low magnification.The conjunctiva represents the first line of defense to a series of pathogens and allergens. Any compromise of this leads to an inflammatory response, which is typically visible as hyperemia.The purpose of the overview is to assess the degree, depth and localization of any excessive redness. Dyes, filters and stains all help in the investigation of any anomaly seen, in addition direct, focal illumination and higher magnification will allow more accurate diagnosis of the problem.

For ease of description between fellow practitioners the conjunctiva can be subdivided into zones. Although useful, a far simpler technique is to indicate any areas of interest on a diagram, particularly as there seems to be a lack of standardization between the various systems that exist. Localization of hyperemia may be a vital clue as to the nature of its cause. For example, a discrete area of dilated blood vessels on the bulbar conjunctiva may indicate a pterygium or phlycten. Interpalpebral hyperemia may indicate dryness or an allergic reaction to an airborne irritant, whereas perilimbal redness may indicate a cornea that is under stress.

The degree of redness can be determined by comparing the clinical observations to a pictorial grading scale or alternatively an intuitive scale as indicated in Table 4.1.

Slit-lamp examination of the anterior segment

If the observations do not quite fit the scale then plus and minus increments can be added to enhance the descriptions.

The vasculature on the ocular surface is best viewed with a red-free filter. It consists of three groups of vessels.These are, in order of increasing depth from the surface: conjunctival, episcleral and scleral. As the vessels move away from the surface they increase in caliber and darkness, with the conjunctival vessels being the smallest and reddest. It is essential to be able to differentiate the depth of any hyperemia in order to distinguish inflammation at each of these levels.This can be done in optical section and moderate magnification by asking the patient to blink. As they do, the superficial conjunctival vessels move, while the deeper episcleral vessels are more resistant. Conjunctivitis tends to produce an intensely red eye and the injection tends to be greatest at the fornices, the vessels which are full of blood appear irregular and can be made to move.They also blanch when mild pressure or topical decongestants are applied. Deeper vessels do not move so readily and do not blanch with slight pressure or decongestants.The hyperemia associated with episcleritis tends to be salmon-pink and usually sectorial. Scleritis produces a purplish hue, which is diffuse and present all the way to the fornices.

Conjunctivitis and episcleritis are relatively superficial inflammations and can either be self-limiting or have some corneal involvement. Scleritis is a deep inflammation and tends to be associated with stromal keratitis and with anterior chamber

General examination of the eye

(AC) activity.The clinician should be aware and should examine

for flare and cells in the AC (see page 70). 57 A general examination of the conjunctiva is easily performed

in a ‘Z’-shaped or zigzag pattern. Scanning across in this way will allow superior, middle and inferior zones to be examined. Following examination of the limbal and bulbar conjunctiva, pulling the lids back to expose the palpebral conjunctiva gives the practitioner access to areas that are normally not exposed. It is far too commonly forgotten to evert the upper as well as the lower lid to view the tarsal and forniceal conjunctiva. It is essential to view this area, as this is the regular haunt of concretions and internal hordeola.These rarely cause any symptoms to the patient, but can be the root of ocular discomfort when they break through to the surface.

Everting the eyelids to expose the conjunctiva in this zone is essential if follicles or papillae are suspected. Follicles are lymphatic in origin and as such are avascular (Figure 4.6).With direct, focal illumination and moderate magnification they appear as moderate-sized, multiple, translucent, rice-shaped elevations. As they grow they displace the conjunctival vasculature, hence they appear to have a vascular tunic surrounding their base.They are usually smaller than papillae.

Figure 4.6 Follicles: note the absence of central vasculature

(after Franklin, A. Reproduced with permission from Doshi & Harvey

Investigative Techniques and Ocular Examination, Butterworth-Heinemann 2003)

Slit-lamp examination of the anterior segment

Papillae have their origin in the conjunctival tissue and consist

58of a central vacular tuft surrounded by a diffuse infiltrate composed of white blood cells (Figure 4.7).They can only occur when the conjunctival epithelium is attached to the underlying levels by fibrous septa. Giant papillae occur when these septa are ruptured (Figure 4.8).The size of papillae varies greatly, but they are larger on average than follicles.

Figure 4.7 Giant papillae showing vascular cores surrounded by infiltrate (after Franklin, A. Reproduced with permission from Doshi & Harvey

Investigative Techniques and Ocular Examination, Butterworth-Heinemann 2003)

Figure 4.8 Giant papillae: fluorescein makes the outline of the cobblestones much easier to see (after Franklin, A. Reproduced with permission from Doshi & Harvey Investigative Techniques and Ocular Examination, Butterworth-Heinemann 2003)

Specific examination of the anterior segment structures

Finding either or both (as they can coexist) does not indicate a

firm diagnosis.The presence of either or both is an indication to 59 investigate further.When fluorescein is instilled the surface

texture is enhanced as the dye aggregates in the channels between the elevations.

Specific examination of the anterior segment structures

Following a general examination of the ocular surface and adnexa it is desirable to utilize all of the varied illumination techniques to assess some of the finer structures of the anterior segment.

These include the cornea, anterior chamber, iris and pupil, lens and the anterior vitreous body.This may be as a part of the routine examination or as a result of specific symptoms reported by the patient.

Examination of the cornea

For the initial examination of the cornea the illumination system should be set at an angle of 45–60° from the observation system and a relatively wide beam should be used in order to create a relatively thick section or parallelopiped (see Figure 4.9).The illumination should come from the same side as the part of the cornea being examined.The clinician then scans across the cornea in a zigzag fashion altering the position of the illumination system ensuring it remains on the side of the area of interest.This method will allow the observer to scan across the cornea in three zones: the superior, middle and lower regions. Using focal, direct (and indirect) illumination allows the clinician to pick up any lesion, which can then be investigated in greater detail using other illumination techniques. Staining the cornea with fluorescein and observing any areas of pooling is also considered an integral part of any routine.

If a lesion is found on the cornea there are a number of factors that need to be determined before the appropriate course of management can be initiated.These include its location, size, density, color and depth.